Track tamping machine



1959 F. PLASSER EI'AL 2,915,018

TRACK TAMPING MACHINE Filed March 7, 1957 2 Sheets-Sheet 1 I N V EN TOR)Fra nz Pmssaz 3 JIM 7/7502 :2

BYgfJ /w F. PLASSER ETAL 2,915,018

Dec. 1, 1959 TRACK TAMPING MACHINE Filed March 7; 1957 2 Sheets-Sheet 21N VENTORS BY 6M2 %;4

arrow United States Patent TRACK TAMPING MACHINE Franz Plas'ser andJosef Theurer, Vienna, Austria Application March 7, 1957, Serial No.644,638 Claims priority, application Austria March 10,, 1956 2 Claims.((31. 104-12) The present invention relates to track tamping machineswhich are movable along railroad tracks to pack ballast under therailroad ties. More particularly, this invention relates to ballasttamping machines of the type wherein vibratory tamping tools arearranged in pairs, each tool being linked to a nut mounted on arotatable threaded spindle whereby the distance between the tampingtools of each pair may be varied by rotating the spindle and therebymoving the nut therealong.

Purely mechanical tamping tool distance varying devices were, foundunsatisfactory because it was not possible to avoid breakage of machineparts, andmore particularly of the distance varying devices, under theincreased pressures encountered in the tamped ballast despite manysafety means developed for the purpose of limiting the maximal densityof the tamped ballast and, accordingly, the pressures to which thedevices were subjected.

Therefore, track tamping machines have more recently been developed, inwhich the tamping tool distance varying devices are hydraulicallyoperated. Machines of the latter type have been particularly successfulwhere the hydraulic cylinder chambers of a complete tamping toolaggregate were connected to a single hydraulic :system so that thetamping tools could be adjusted individually, independently from eachother and asynchronously ac cording to the resistance encountered byeach tool in the ballast. 7

While the hydraulically-operated devices had many advantages, it wasfound diflicult to make the center of vibration of the tamping tools,:i;e. the theoretical point of rest during their vibrations, coincidewith the *connecting pivots linking the tools to the hydraulicallymovedactuating elements. For, instance, in our application Serial No.462,086, filed October 13, 1954, now Patent No. 2,876,709, the tampingtools are linked to cylinders which are slidably mounted :onpistonsdividing the cylinders into two chambers. While it was possible to holdthese cylinders more or less .in .place by maintaining both -cylinderchambers under constant pressure and to effect sliding movement ofthe'cylinders by increasing the pressure in one of the chambers, thenecessary damping of residual vibrations nevertheless requiredadditional devices to meet practical operating conditions.

,It is the principal object of the present invention to provide a tracktamping machine wherein the advantages of the mechnical and hydraulicoperation of the tamping tool distance varying devicesare' combinedWhile the respective disadvantages of each of these prior systems arefully tavoided.

This object is obtained in accordance with this invention by moving thetampingtools with rotatable threaded spindles whichare driven byhydraulically-operated transmission means. Preferably, each tamping toolhas its own, separately rotatable spindle and, accordingly, its ownhydraulically operated driving means so :that the tools may be adjustedasynchronously and individually 2,915,018 Patented Dec. 1, 1959 ice inresponse to the pressure encountered by each tool in the ballast. Theseparate driving means for each tool of a tamping tool aggregate arepreferably connected to a single hydraulic fluid pump and areinterconnected by a single conduit system.

The prior hydraulically-operated tamping tool distance varying deviceshad additional. disadvantages. While the tamping tools remainedimmobile, the hydraulic fluid coming from the continuously operatingpump had to be returned to the fluid storage tank by means of safetyvalves mounted in the fluid conduit to delimit the maximum pressuretherein. During extended operations, the passage of the fluid throughthe safety valve caused it to be undesirably heated. Furthermore, whilethe tamping tool's stood idle, the entire driving energy applied to thepump was uselessly, wasted.

A similar waste of energy was encountered in the mechanically operateddevices hereinabove described. While the tamping tools were at rest,i.e. when theywere prevented from further movement by lateral stopsprovided for this purpose, the mechanical driving elements weresubjected to increased wear.

In accordance with a preferred feature of the invention, therefore, aninfinitely variable pump is provided to supply hydraulic fiuid to thespindle driving means. The capacity or delivery rate of this pump isautomatically varied between zero and a predetermined maximum by thepressure the moving tamping tools encounter in the ballast or at a stop.

The above and other objects, features and advantages of the presentinvention will be more fully explained 'in the following detaileddescription of a now preferred embodiment thereof, taken in conjunctionwith the accompanying drawing which illustrates certain structuraldetails without limiting the invention thereto. In the drawing,

Fig. l'is aside view, partly in section, of the front part of 'a tracktamping machine;

Fig. 2 schematically illustrates the hydraulic fluid conduit and controlmeans actuating the driving mechanism for the spindle of each tampingtool;

Fig. 3 is a sectional view of the hydraulic fluid pump; and.

Fig. 4 shows a detail of the pump control means.

Referring now to Fig. 1, there is shown a track tamping machine movingon track 42 mounted on ties 43 which are supported in ballast 41.. In amanner well knownper se, the tamping tool carrier 3 is verticallyslidably supported on posts 2 mounted in the carriage frame.Eccentric'shaft 5 is journaled in the carrier 3 and vibrates the tampingtools 4 by reciprocating or oscillating tool mounting arms '6 when theshaft is rotated. The tamping tools are pivoted to arms 6 at their upperends. .All .this structure is conventional and is described, forinstance, in our above-mentioned patent application.

The mechanism for varying the relative distance of the tamping tools 4will now be described.

Each tool is pivoted intermediate its ends at 10 to a longitudinallys'hiftable nut 7 mounted on a rotatable threaded spindle 8. The spindlesare rotatably journaled in bearings '8 and 8", 8 being centrally mountedto receive the inner ends of two adjacent spindles controllingthemovement of one pair of tamping tools and a bearing 8" being mountedfor receiving the outer end of each tool. For added stability, anintegral portion 7 of each nut is slidably supported and guided onlongitudinal guide rod 9 rigidly mounted in tamping tool carrier 3.

The outward and inward movement of tamping tools 4, which are pivotablylinked to nuts 7 at 10, is limited by suitable stops mounted forcooperation and engagement with nuts 7 when the same have reached theposition of the stops. The outer :stops are shown 'at 1 Such a. deviceis shown,

and 11', stops 11 being removable from guide rod 9 to permit a wideroutward stroke of the tamping tools to fixed stops 11'. This isdesirable in case of tamping wider ties. A'preferred arrangement formoving stops 11 is described and claimed in our copending applicationSerial No. 629,183, filed December 18, 1956, now Patent No. 2,872,878.

A gear wheel 15 is keyed to each rotatable spindle 8 outside bearing 8",each gear 15 meshing with a gear wheel 14 which, in turn, is engaged bypinion 13. This gear transmission serves to transmit rotary motion fromthe hydraulically operated drive 12 to the associated spindle 8.Hydraulically operated driving systems which convert the hydraulicpressure of a fluid supplied to it under pressure by a pump, forinstance, into a rotary motion like a turbine are well known per se.Many types of such hydraulically operated rotary driving systems areknown and, since their specific structure is of no importance in respectof the present invention, they are not further described so as to limitthe description to the specific improvement provided by this invention1.

The supply conduit system of hydraulic fluid, such as oil from storagetank 18 to the driving systems 12 is schematically illustrated in Fig.2. Pump 19 is mounted on the tamping tool carrier 3 in supply pipe 16which leads from the oil storage tank to the pump. The hydraulic fluidis delivered through pump output pipe 21 to the cylinder 22 which housesa slidable rod with a plurality of pistons 23 to regulate the fluidsupply to the driving systems 12. Return pipe 26 is connected tocylinder 22, leading back to the oil storage tank.

As shown in Fig. 2, there are four driving systems with their pinions 13to drive the associated spindles 8 moving the four tamping tools of atool aggregate adapted to tamp ballast at both sides of track 42. Supplyconduit systems 24 and 25 lead from cylinder 22 to each of the drivingsystems 12. The slidable rod with its pistons 23 is reciprocable incylinder 22 by actuating the lever 27. A branch pipe 28 leads from pumpoutput pipe 21 to a control element which consists of cylinder 29housing piston rod 31 with piston 30. The piston is biased by spring 34.The piston rod is linked to rod 32 which engages pin 33 mounted on thepivotable element 20 of pump 19, the pin cooperating with longitudinalslot 32' of rod 32 (see Fig. 4).

Another branch pipe 35 leads from supply conduit 25 to a second controlelement consisting of cylinder 36 housing piston rod 37 with piston 37.Piston 37 is biased by spring 38. Piston rod 37' is connected to rod 39which also engages pin 33 with its longitudinal slot 39' (see Fig. 4). iThe pivotable element 20 of the pump is biased by spring 40 connected toits outer end and to the tamping tool carrier to hold the element 20normally at an angle in position I (see Fig. 3).

Infinitely variable pumps are well known and have been used for manypurposes where it is desired to adjust the pump delivery rate orcapacity smoothly and gradually. A preferred pump of this type is shownin Fig. 3.

Pump drive shaft 17 is journaled in the fixed pump portion 19, inletpipe 16 and output pipe 21 being connected to portion 19 at oppositesides thereof. Cylinder 19" is mounted on pump portion 19 and glidablyhouses two pistons 19' whose piston rods are connected to pivotable pumpportion 20 by means of universal X joints 20". The pivotable pumpportion is mounted on cylinder 19" by means ofa shaft with the universaljoint 20'.

Position I indicates the maximal angle of pivotable pump element 20, atwhich point the capacity of the pump is also at a maximum because thelength of the stroke of pistons 19' is at a maximum. vIn position H, thepump portions are coaxial and the pump will deliver for instance inLetters Patent No. 956,570, dated May 3, 1910.

v 4 a no fluid during rotation because the length of the piston strokesis zero in this position.

The tamping tool distance varying mechanism of the invention operates asfollows:

When the track tamping machine is moved into tamping position so thatthe pairs of tamping tools forming the tamping tool aggregate are placedover a tie and the tamping tool carrier is lowered to position the lowerends of the tamping tools into the ballast, as shown in Fig. 1, controllever 27 is thrown into position A (full lines). In this position, therotating pump will deliver hydraulic fluid, i.e. oil, through outputpipe 21 to cylinder 22 whence the fluid will flow under pressure throughconduit system 24 into the four driving systems 12. The hydraulicpressure in the driving systems will rotate pinions 13 and accordinglymeshing gears 14 and 15. The direction of rotation of pinions 13 is soselected in this case that the corresponding rotation of spindles 8 willforce nuts 7 and tamping tools 4 inwardly so that the ballast betweeneach pair of tools is tamped under the tie. After the hydraulic fluidhas exhausted its pressure in the driving systems, it will leave themthrough conduit systems 25 and will return without pressure to storagetank 18 by way of return pipe 26.

As soon as the approaching movement of the tamping tools hassufficiently densified and compressed the ballast therebetween, i.e.when all tamping tools 4 encounter the same resistance in the ballast,regardless of the individual position of each tool, the pressure inconduits 21 and 24 will correspondingly increase. This, on the otherhand, will also cause a pressure increase in branch pipe 28 so thatpiston 30 of the first control element will slowly be pressed downwardlyagainst the load of spring 34 as the pressure in pipe 28 mounts. Themovement of the piston will actuate a corresponding movement of rods 31and 32 which will force down the pin 33, thus displacing the pivotablepump portion 20 against the bias of spring 40. As pump portion 20 isslowly moved toward axial alignment with pump portion 19, acorrespondingly slow reduction of the pump delivery rate will graduallytake place.

The characteristics of spring 34 are preferably so chosen that thatpressure in conduit system 24 and, therefore, the compression force oftamping tools 4 increases slowly.

Finally, when the maximal pressure has been reached, the pivotableportion 20 is moved into axial alignment with the pump portion 19 sothat the pump is in position II. In this position, no further fluid isdelivered by the pump. Thus, the pump will use no energy when thetamping tools stand still or only so much energy as is required tomaintain the pressure in the conduits.

It will be seen that this hydraulic conduit system requires no safetyvalves since the fluid flow automatically stops when the tamping toolsare at rest.

When tamping is completed and it is desired to move the tamping toolsapart again, the control lever 27 is thrown into position B (brokenline). In this position, pistons 23 will so divide cylinder 22 that pumpoutput pipe 21 communicates with conduit system 25 while conduit system24 is in communication with fluid return pipe 26.' Since there is verylittle resistance to the opening movement of the tamping tools, thehydraulic pressure in pipe 28 and cylinder 29 will decrease considerablyso that the pivotable pump portion 20 may return to its normal positionI under the bias of spring 40. Thus, the pump again delivers oil throughoutput pipe 21 into cylinder 22 and conduit system 25 to each of thedriving systems 12, the pinions 13 now being rotated in the oppositedirection to reverse the rotation of spindles 8 and move the tampingtools 4 apart. Since there is little resistance in the path of theopening tamping tools, this movement is effected relatively rapidly. Thereturn of the exhausted hydraulic pressure fluid from systems 12 to theoil storage tank is eflected through conduit system 24. As soon as thenuts 7 or their upper parts 7 encounter stops 11 or 11' during theoutward movement of the tamping tools, increased pressure is immediatelycreated in conduit system 25. This causes a correspondingly increasedpressure in branch pipe 35 and cylinder 36 of the second controlelement. The increased pressure will move piston 37 and piston rod 37'downwardly and pulls down the pivotable pump portion 20 which isconnected to rod 37' by means of rod 39 and pin 33. Thus, portion 20 isslowly depressed against the load of spring 38 in cylinder 36 and spring40 which is biased to hold portion 20 under angle a.

As above described, the pump delivery rate is thus slowly decreased tozero. When the tamping tools are at rest, the pump will also stop untilcontrol lever 27 is thrown into position A again to start a new tampingcycle.

The second control element 36, 37, 38' is so dimensioned and arrangedthat it responds much more quickly to increased pressure in the pipe 35than the first control element 29, 30, 34 responds to increased pressurein pipe 28. The reason for this is that the first control element isdesigned to become effective during the tamping movement of the tampingtools, i.e., at high pressure, while the second control element shouldact quickly during the pressureless opening movement of the tampingtools.

Fig. 4 illustrates the purpose of elongated slots 32' and 39 used toconnect the above control elements to the pivotable pump portion 20.With this arrangement, each control element can act upon pin 33 ofportion 20 independently of the other control element, i.e. the rod 32can depress pin 33 by the length of slot 39' without moving rod 39 whilerod 39 can pull the pin down by the length of slot 32 without disturbingrod 32.

As will be clear from the above description, the present invention isbased on the concept that unexpected improvements in a tamping tooldistance varying mechanism can be achieved when the known tool spindledrives are actuated hydraulically, inasmuch as such an arrangementavoids all the disadvantages of the purely mechanically operated driveswhile eliminating the faults of the newer purely hydraulic drive means.

While a preferred embodiment of the new andimproved tamping tool spacingadjustment mechanism has been described and illustrated in detail, itwill be clearly understood that many modifications and variants of thedescribed principle of combining a mechanical and hydraulic drive mayoccur to the skilled in the art, particularly after benefiting from ourteaching, without departing from the spirit and scope of the inventionas defined in the appended claims.

What we claim is:

1. A mechanism for varying the relative distance between two tampingtools of pairs of opposing vibratory tools of a track tamping machinewherein the tamping tools are mounted on a carrier and reciprocateparallel to the track, and means is arranged on the carrier forimparting a reciprocating vibratory motion to the tamping tools,comprising, in combination: a rotatable threaded spindle mounted on thecarrier substantially parallel to the track, a nut mounted on thespindle and linked to an associated one of said tools at a pointintermediate its ends whereby said nut constitutes a dead centersubstantially free of vibrations for said tool, a hydraulicallyoperateddriving system mounted on the carrier, mechanical power transmissionmeans connecting said driving system with the spindle for rotating thesame, the hydraulically dn'ven spindle constituting the sole positivedrive for reciprocation of said nut andits associated tool, and amaximum amount of vibratory force being transmitted to said tool whilethe nut constituting the dead center thereof is reciprocated, and meansfor supplying hydraulic pressure fluid to the system.

'2. The mechanism of claim 1, wherein the hydraulically-operated drivingsystem includes a separate drive for each spindle and the hydraulicpressure fluid supply means comprises a single fluid pump and fluidconduit system interconnecting the separate spindle drives, andcomprising means for reversing the direction of rotation of each spindledrive, said reversing means comprising an adjustable control valveconnected in the fluid conduit system between the pump and the separatespindle drives, said conduit system including two separate conduits eachconnected between the control valve and all spindle drives, and meansfor adjusting the control valve to connect selectively one and the otherof said two separate conduits to the pump.

References Cited in the file of this patent UNITED STATES PATENTS2,791,971 Schnellmann May 14, 1957 FOREIGN PATENTS 285,504 SwitzerlandDec. 16, 1952 1,029,682 France Mar. 11, 1953 1,101,408 France Apr. 20,1955

